Fluoropolymer compositions that may be cured in stages or steps are known in the art. U.S. Pat. No. 4,177,223 to Arhart et al. discloses a fluoropolymer composition containing a blocked crosslinking agent, i.e. one in which the hydroxyl groups are reacted to form acetal or thioacetal groups and participates in the vulcanization reaction primarily at high temperatures, and a crosslinking agent, that participate in the vulcanization reaction at lower temperatures. One difficulty with this prior art composition is that during the high temperature crosslinking reaction the blocking agent is released to the atmosphere as a pollutant.
Fluoroelastomer compositions containing more than one vulcanization component are known. U.S. Pat. No. 3,655,727 to Patel et al. shows (See Table K) fluoroelastomer compositions containing hydroquinone and aromatic diamines which compositions are cured by heating in a mold (press cured) and then in an air oven at a higher temperature (postcured).
The composition and process of the present invention is an improvement over the prior art, in that the curing of the compositions does not release a polluting blocking agent fragment, and in that the compositions contain a vulcanization component that is active under press cure conditions and another component that is appreciably active only under post cure conditions.